1. Field of the Invention
The present invention relates to a lighting control apparatus for a photographing apparatus, and in particular to improvement of a lighting action during a long exposure operation.
2. Description of the Related Art
A lighting device which uses LEDs is proposed, in place of a lighting device which uses strobe radiation such as a xenon pipe which has been widely used with photographing apparatus, such as a camera. LEDs can be driven at a low voltage, and the circuit construction of the LED is simple.
When a rectangular wave signal is used to drive the illumination of the LED, the problem of the radio wave interference occurs because the high-frequency component is included in the rectangular wave signal.
Japanese unexamined patent publication (KOKAI) No. 2002-072166 discloses a controlling circuit which controls the output of signals, where the rectangular wave signal has a rising time and a falling time. Emission of light from the lighting source is gradually increased during the rising time, and emission of light from the lighting source is gradually decreased during the falling time, in order to restrain the high-frequency component of the rectangular wave signal, in the LCD display device.
However, when the above-discussed Japanese unexamined patent publication is applied to the lighting device for the photographing apparatus, an error of the light quantity due to the rising time and the falling time of the rectangular wave signal, occurs. The error of the light quantity influences the supply of light which is needed to illuminate the photographic subject.